Update.
[glibc.git] / nis / nis_hash.c
blobddd91515b0e5fa663e82b9b8f62ffc5dc3782b95
1 /* Copyright (c) 1997, 1998, 1999, 2004 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Thorsten Kukuk <kukuk@suse.de>, 1997.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18 02111-1307 USA. */
20 #include <rpcsvc/nis.h>
22 /* This is from libc/db/hash/hash_func.c, hash3 is static there */
24 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
25 * units. On the first time through the loop we get the "leftover bytes"
26 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
27 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
28 * this routine is heavily used enough, it's worth the ugly coding.
30 * OZ's original sdbm hash
32 uint32_t
33 __nis_hash (const void *keyarg, register size_t len)
35 register const u_char *key;
36 register size_t loop;
37 register uint32_t h;
39 #define HASHC h = *key++ + 65599 * h
41 h = 0;
42 key = keyarg;
43 if (len > 0)
45 loop = (len + 8 - 1) >> 3;
46 switch (len & (8 - 1))
48 case 0:
49 do {
50 HASHC;
51 /* FALLTHROUGH */
52 case 7:
53 HASHC;
54 /* FALLTHROUGH */
55 case 6:
56 HASHC;
57 /* FALLTHROUGH */
58 case 5:
59 HASHC;
60 /* FALLTHROUGH */
61 case 4:
62 HASHC;
63 /* FALLTHROUGH */
64 case 3:
65 HASHC;
66 /* FALLTHROUGH */
67 case 2:
68 HASHC;
69 /* FALLTHROUGH */
70 case 1:
71 HASHC;
72 } while (--loop);
75 return h;